Tamping machines are used to repair and correct the ballast around and beneath railroad ties so that the road bed can uniformly support the passage of railroad trains over it. Tamping machines are designed to move along the road bed and to force at least eight tamping pads into the ballast, one pad on each side of each tie on each side of each rail. The tamping pads are then vibrated and moved toward the tie in unison to compact the ballast under the tie and provide a firm foundation around and beneath the tie. The railroad bed, in turn, provides a solid foundation for the heavy loads encountered as a train passes thereover.
A typical problem encountered by the tamping tools currently available is that the typical ballast materials are highly abrasive, i.e., sand and ballast rock, gravel and cinders. The leading edges of the tamping pads wear away extremely rapidly and, when partly worn, are deficient for carrying out the tamping and squeezing operations efficiently. Thus, the tamping pads must be replaced or the leading edges of the tamping pads rebuilt.
It is known in the art to face the edges of the tamping pads with a high chromium-steel braze to provide added wear resistance. Even with chromium-steel facing, a normal run of the tamping machine is only four to six miles of road bed before the edges of the tamping pad are worn to the point where replacement is necessary for efficient operation.
The wear life of the tamping pad has been substantially increased by providing a tamping pad consisting of a tamping blade and a tungsten carbide insert in the leading edge of the tamping blade. Such a tamping blade is described in U.S. Pat. No. 3,793,960, which is assigned to the assignee of the present invention. This patent teaches a carbide insert which is nested and brazed into a groove formed in the leading edge of the tamping blade. The carbide insert is of sufficient bulk and is adequately supported to avoid chipping, cracking and spalling of the insert under the heavy impact loading to which the leading edge of the blade is exposed.
While it has been found that the construction of the tamping tool according to U.S. Pat. No. 3,793,960 substantially increases the life of the tamping blade, it remains a continuing objective in the industry to increase the wear life of the tamping tool. Another attempt to increase the life of the tamping blade is found in U.S. Pat. No. 3,971,323, entitled "Tamping Blade and a Hard Wear-Resistant Insert Therefor," to Richard W. Beiswenger. This patent teaches a tamping blade having a plurality of wear-resistant inserts positioned end to end in a cut out at the leading edge of a blade shoe of steel. Each insert according to this patent has first and second opposed sides and first and second opposed major surfaces with the major surfaces being angular to each other to provide a substantially uniform thickness to the body at each of these sides. The first side of each insert has a thickness of at least about 3/8 inch and is adapted to provide a leading edge for the tamping blade extending across the thickness of the tamping blade beyond the leading edge thereof. The first major surface is adapted to provide a wear resistant facing for the tamping blade during lateral movement. While the tamping tool of U.S. Pat. No. 3,971,323 does provide advancement to the art of tamping tools and provides a longer useful life than the conventional practice of utilizing a high chromium-steel braze to provide adequate wear resistance, limitations still exist in the wear-resistant inserts.
The present invention overcomes these difficulties and disadvantages and provides a tamping pad with a substantially prolonged useful life. A tamping pad according to this invention provides a tamping blade with carbide inserts. The tamping blade has an interrupted leading edge defined by a plurality of arcuate edges along the entire leading edge of the tamping blade. Moreover, the tamping blade of this invention in combination with the insert design, significantly enhance the useful life of a tamping blade.